Annulus thickness

Figure 24. Annulus thickness vs system pressure. (Calculated from model of Yang.)...

Based on this equation one can predict the temperature increase to be expected for a defined annulus thickness as shown in Fig. 3. With the above-described approach one can in addition construct a monolithic annulus of a desired radius but limited thickness. By preparing a series of annuluses where the outer diameter of the smaller monolith is equal to the inner diameter of a larger one, a large volume monolithic unit can be constructed by forming a so called tube in a tube system, as shown in Fig. 4. In this way, a monolithic unit of the required volume and uniform pore size distribution can be prepared. Furthermore, the voids between the annuluses can be filled with the reaction mixture and polymerization is allowed to proceed for a second time. Since the voids are very thin, no increase in temperature during the course of the reaction is expected. 

Fig. 3. Effect of the annulus thickness on the maximal temperature increase during the polymerization of a GMA-EDMA monolith. Inner annulus radius is 10 mm calculation is based on Eq. (10). (Reprinted with permission from Podgornik A, Barut M, Strancar A, Josic D,Koloini T (2000) Anal Chem 72 5693)...

The release profile depends on 1) the annulus thickness, ie. the internal and external diameters 2) the swelling solution concentrations, both inside and outside the suppository 3) the period of swelling both inside and outside 4) the composition of the hydrogel which determines the water uptake and consequently the permeability of the drug through the matrix. 

Sulphur annulus thickness this is determined by the energy/ power output required, the desired cell resistance and the time available for recharge. Safety considerations are also important. 

The reactor downcomer annulus surrounding the core block is modeled as a pipe component. Per Table 12-8, the downcomer flow area is based on the annulus thickness (0.0254 m) and the core block diameter (0.575 m) (Reference 12-15). Therefore, the downcomer flow area is 0.04791 m with a hydraulic diameter of 0.0508 meters. 

For determining in solid or hollow round sections it is essential to first determine the self geometric mean distance, of the conductors which varies with the thickness / (annulus) of the conductor, approaches its outer radius, ri. in an infinitely thin conductor and to O.TTSri in a solid bar. This variation, in the form of D lr is drtiwn in Figure 28.21, as a function of r,// . 

Current rating varies with the surface area of a conduelor and its thickness (annulus). In our sample calculation, to establish the basic parameters of the conductor and the enclosure, we have considered the current density for both as 400 A/inch. ... 

Consider a converging annulus of thickness, h, and radius, a, within the die. If the angle of convergence is <(> then simple geometry indicates that for uniform convergence... 

Ej(r) and, therefore, indicate better adhesion, since, in such cases, the thickness of the mesophase annulus Ar is more and more reduced. 

Various correlations for mean droplet sizes generated by air-assist atomizers are given in Table 4.6. In these correlations, mA is the mass flow rate of air, h is the height of air annulus, tf0 is the initial film thickness defined as tj ) = dQw/dan, d0 is the outer diameter of pressure nozzle, dan is the diameter of annular gas nozzle, w is the slot width of pressure nozzle, C is a constant related to nozzle design, UA is the velocity of air, and MMDC is the modified mean droplet diameter for the conditions of droplet coalescence. Distinguishing air-assist and air-blast atomizers is often difficult. Moreover, many... 

Annular orifices can also be used to advantage for gas metering when there is a possibility of entrained liquids or solids and for liquid metering with entrained gas present in small concentrations. Coefficient K was found by Bell and Bergelin [Trans. Am. Soc. Mech. Eng., 79, 593-601 (1957)] to range from about 0.63 to 0.67 for annulus Reynolds numbers in the range of 100 to 20,000 respectively for values of 2L/(D — d) less than 1 where L = thickness of orifice at outer edge, D = inside pipe diameter, and d = diameter of orifice disk. The annulus Reynolds number is defined as... 

To reduce interference from Compton scattering, an anticoincidence shield, 76 cm. X 76 cm., was constructed as shown in Figures 2 and 3. The shield consists of two independent type NE-102 plastic phosphor annuli. A 10-cm. bore through the top annulus accommodates the Ge(Li) detector chamber and the cryogenic assembly. The bottom annulus (i.d. diameter 25 cm.) houses a 20-cm. diameter by 15-cm. thick Nal(Tl) scintillator. Normally, the plastic phosphor is used in conjunction with the Nal(Tl) to form a well -shaped anticoincidence shield. Altema-... 

Twelve RCA type-8055 photomultipliers are attached to the surface of the top annulus. The bottom annulus, which has the larger bore, has 8 photomultipliers of the same kind. A Nal light pipe 7.5 cm. thick couples four RCA type-8054 photomultipliers to the Nal(Tl) scintillator. 

Determine the thickness of the down-flowing water annulus. 

B1 - B2 These cells contain the values of the variable names in cells A1-A2. The association of the numbers in B1-B2 with the names in A1-A2 is accomplished with the INSERTJMAMEJDEFINE command. (The syntax INSERT NAMEJDEFINE means to use the INSERT pull-down menu, followed by the DEFINE and NAME sub-menus. In many cases there are also convenient keyboard shortcuts that avoid actually using the pull-down menu.) As much as possible, it is important to define names that appear in subsequent formulas. It is very difficult to read and debug a spreadsheet that is programmed entirely with explicit cell references. The variable name for the annulus gap thickness Delta r is in A3 and the value is computed in B3 as = r.out - r in. 

The permeable barrier was composed of a steel frame that was constructed to hold the SMZ and to allow for media replacement. The frame was constructed of 5-cm steel angle iron and 2.5-cm and 7.6-cm square steel tube. The frame had solid floor and end walls (1.3-cm-thick steel plates) to divide it into three distinct cells. Each cell had perforated metal walls (0.16-cm thick perforated steel sheets with 0.64-cm holes covering 50% of the surface area) transverse to the direction of flow. The perforated metal was installed on both the inside and the outside of the steel tube skeleton, resulting in a 7.6-cm-wide annulus between the inner and outer walls of the frame. The entire frame assembly was professionally painted with high-quality, rust-resistant paint. The barrier frame was placed in the pilot-test tank in three sections on top of a 1-m depth of aquifer sand that had been previously added to the tank in lifts. The physical and chemical properties of the sand are described later in this chapter. The three frame sections were bolted together after applying a silicone caulk (Sika-Flex ) for sealing. The end of the barrier in contact with the side of the tank was sealed to the... 

One important aspect of wire-coating is the thickness distribution of the polymer on the surface of the wire as well as the velocity distribution within the die. A simplified wire coating process is presented in the Fig. 6.37, where the wire radius is defined by R and the annulus radius by kR. This type of flow is often referred to as an axial annular Couette flow. 

Profiles are all extruded articles having a cross-sectional shape that differs from that of a circle, an annulus, or a very wide and thin rectangle (flat film or sheet). The cross-sectional shapes are usually complex, which, in terms of solving the flow problem in profile dies, means complex boundary conditions. Furthermore, profile dies are of nonuniform thickness, raising the possibility of transverse pressure drops and velocity components, and making the prediction of extrudate swelling for viscoelastic fluids very difficult. For these reasons, profile dies are built today on a trial-and-error basis, and final product shape is achieved with sizing devices that act on the extrudate after it leaves the profile die. 

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